NOT APPLICABLE
This invention relates generally to power semiconductor devices, and more particularly the invention relates to a power semiconductor current limiting device and a method of making same.
It is known to protect electrical circuits against high input currents by means of a current limiter. A current limiting device works in series with an electrical circuit, contributing a low serial resistance, Ron, below a given specification. When the circuit is overloaded or malfunctioning, such as output short circuit, resulting in a high current mode outside of normal operation, the current limiting device serves to clamp the current flowing through the circuit, Ilim, within a given allowance, xcex94Ilim, until the voltage across the current limiting device exceeds its specified operating limit, Vbr. When made by the method taught in the present application, the device provides low Ron, high Ilim, low xcex94Ilim, and high Vbr with a wide range of desired Ilim that is easy to adjust by controlling certain implant energy or dose. FIG. 1 shows these critical parameters in graphical form.
The present invention is directed to a current limiting device having improved current-voltage characteristics including a lower Ron, higher Ilim, lowerxc2x1xcex94Ilim, and higher Vbr.
In accordance with the invention, a vertical MOS current limiting device has a modified dopant implant. More particularly, in one embodiment serial resistance, Ron, can be controlled by a shallow P dopant implant and the current limit, Ilim, can be controlled by a deeper P-dopant implant. The current limiting function is achieved by the overlap of depletion regions by biasing the P-dopant implanted regions.
The invention and objects and features thereof will be more readily apparent from the following detailed description and appended claims when taken with the drawings.